1. Field of the Invention
The present invention relates to a fan control system and in particular to a fan control system controlling a plurality of fans.
2. Description of the Related Art
In general, device fans normally run when a power is supplied. The power can turn the fan on or off but the power cannot provide other control functions which are provided by a coupled controller such as multiple operating speeds controller. FIG. 1 is a schematic view of a conventional fan control system. Controller 10 is coupled to and controls fans 12a˜12n in a parallel fashion, such that flexibility of the fan control system is reduced.
Additionally, the controller 10 can only control a limited number of fans and the number of controllers increase with the number of fans or output signals thereof, such that costs of the fan control system increase.
FIG. 2 is a block diagram of a fan as disclosed in U.S. Pat. No. 6,318,965. The CPU 62 of the exemplary host machine 50 is also shown to have a memory 66 and a connection via the system bus 64 to a storage subsystem 68. The fan 52 comprises a controller 56, a temperature sensor 74, and a fan motor 76. The temperature sensor 74 senses a temperature and sends a temperature signal to the controller 56, the controller 56 alter the rpm of the fan motor 76 according to the temperature signal.
If the temperature sensor 74 is not included within the fan 52, the host machine 50 dynamically passes temperature data to the fan 52 via system bus 64. The controller 56 alters the rpm of the fan motor 76 according to the passed temperature data.
Although the controller 56 alters the rpm of the fan motor 76 according to the temperature signal sent by the temperature sensor 74 or the temperature data passed by the host machine 50, the controller 56 does not monitor and amend fan 54.
FIG. 3 is an electronic system as disclosed in U.S. Pat. No. 6,725,132. Each cooling fan 242, 244, 246, and 248 has a microcontroller to detect failures of other cooling fans 242, 244, 246, and 248. Although each cooling fan 242, 244, 246, and 248 has the ability to detect and compensate for other failed fans by increasing its fan speed, each cooling fan 242, 244, 246, and 248 cannot directly control fan speed of the other fans. Therefore, cooling fan 242, 244, 246, and 248 still only are controlled by user system 140 and power source 210.